It is known to prepare bisphenols by reacting a phenol with a carbonyl compound in the presence of a substantially water-insoluble cation-exchange resin containing sulfonic acid groups. See, for example, British Pat. No. 849,965. It is also known to use modified resin catalysts in the above process. Modification may be carried out by either partially esterifying the resin with a mercapto alcohol as described in British Pat. No. 937,072, or by partially neutralizing the resin with an alkyl mercaptoamine as described in British Pat. No. 1,183,564.
A new class of modified resin catalysts has now been discovered which is useful in the above process. This new class of resin catalysts contains a plurality of sulfonic acid groups and a plurality of cyclic mercaptoamine sulfonic acid salt groups.